1. Field of the Invention
This invention relates to a process for the production of electrical energy from the neutralization of aqueous acid and base streams in a cell having a bipolar membrane.
2. Description of the Prior Art
Electrochemical cells useful for the interconversion of chemical and electrical energy are well known in the prior art. When at least two distinct regions, e.g., unit cells or half cells, having unequal chemical potentials are connected ionically through suitable dividers at least semiporous to ion current flow and electrically through a suitable electrical connecting means between electrodes in contact with these regions, electrical energy, i.e., electron current is allowed to flow through the electrical connecting means. Unequal chemical potentials created by differences in concentration or differences in electron-acceptance i.e., reducibility, and electron release, i.e., oxidizability, are well known to one of ordinary skill in the art.
Recent advances in bipolar membrane technology have allowed production of commercially important acids and based from neutral salts by electrodialytic water-splitting. For example, U.S. Pat. No. 3,787,304 describes a process for the production of hydrofluroic acid and hydroxide base by electrodialytic water-splitting of fluoride salt in a bipolar membrane cell. However, the production of electrical energy by spontaneous neutralization of aqueous acid and base streams is not taught.
Zeigerson and deKorosy (Israel Journal of Chemistry, 9 (No. 4), pp. 483-97 (1971).) conducted rectification experiments with a bipolar membrane cell and disclose that a small amount of electrical power can be generated from acid-base neutralization across a bipolar membrane when acid is on the anion permeable face and base is on the cation permeable face of the membrane. However, the cell does not operate reversibly and does not generate commercially significant quantities of electrical power.
Japanese Pat. No. 50-83735 discloses cells constructed with carbon electrodes positioned in aqueous acid and base solutions separated by a porous diaphragm. Although this diaphragm permits neutralization and buffering between the acid and base solutions, the cell operates without bipolar membranes to generate electrical enery from spontaneous oxidation-reduction reactions at the electrodes.
While it is known in the prior art that dissociation of a salt into an acid and a base requires the input of electrical energy, the prior art has not recognized any efficient method to create, collect and employ electrical potential differences from neutralization reactions of acids and bases.
It is accordingly an object of the present invention to provide a process for the production of electrical energy from the spontaneous neutralization of aqueous acid and base at a bipolar membrane.
It is another object of the present invention to provide a process which generates significant electrical energy by coupling spontaneous neutralization reactions in a bipolar membrane cell with energy-supplying or energy-demanding electrodes.
It is a further object of this invention to provide a commercially useful, regenerative process for electrical energy storage to permit leveling of power loads on electric utility generating plants.
It is a still further aim of the present invention to produce commercially useful electrical power from spontaneous neutralization of acidic and basic industrial effluent streams and from process neutralization used in chemical manufacture.
Additional objects and features of the present invention will become apparent from the disclosure which follows.